Random discovery: Why the 13th Hex character of Guids is ‘4’

I noticed something strange in Sitecore; for most of my nodes (not the Sitecore node!), the 13th Hex character of the identifying GUID is ‘4’.

I had a list of about 50 of these, and my eye was drawn to the pattern. Now, I thought Guids were entirely random, except that the chance of 50 page template IDs all having a 4 at that character was infinitesimal.

Weird. Except it turns out that they’re not random. I had no idea that there are different versions of guids, or than that character defined the version of the GUID.

This requires a test, so I wrote a program to print Guid.NewGuid() a lot:

All of them are 4s.

So:

  • GUIDs aren’t entirely random.
  • They might not be very random at all, looking at some of the other GUID versions.
  • Which is why they shouldn’t be used as a source of entropy for encryption.
  • I still have things to learn.
Random discovery: Why the 13th Hex character of Guids is ‘4’

Keeping the size of of Sitecore Azure Backups under control

I’ve written before about Azure Backup fails due to Content Testing Screenshots not clearing and the resulting problems with backup size.

That’s not the whole problem though.

Sitecore made some effort to configure some directories to be outside the home folder of the app services, and therefore not subject to backup – but there’s still a lot that shouldn’t be in the backup. Continue reading “Keeping the size of of Sitecore Azure Backups under control”

Keeping the size of of Sitecore Azure Backups under control

Application Initialization for Azure Service Apps (and Sitecore)

We have been having a problem with Sitecore in Azure PAAS – it appears that when auto-scaling scales out, App Services are being put into rotation before they have started up. This is causing all sorts of weirdness.

Sitecore support recommended making sure that we had Application Initialization configured. That seems a good idea. I’m not sure why the guys who set up this instance didn’t; perhaps they were unaware of it (and to be fair, it’s something I’ve not looked at before).

Continue reading “Application Initialization for Azure Service Apps (and Sitecore)”

Application Initialization for Azure Service Apps (and Sitecore)

My problems with Sitecore FXM

Sitecore’s Federated Experience Manager (FXM) allows non-Sitecore sites to record analytics data into Sitecore. It’s both quite neat, and has a number of problems. I’m going to assume you’ve done a little reading about FXM already, but here’s how it works (in Sitecore 9.0.x).

FXM works by having you adding a JavaScript reference to your pages:

This JavaScript, when run, instantiates a JavaScript Object (a Beacon) which makes a request of Sitecore:

And the response to that sets up a Sitecore Session ID, Contact ID, and returns element matches, which are stored in Cookies:

The element matches use HTML Element IDs to identify content to a) attach click handlers too, or b) elements to insert content around or in place of.

This is where we hit the first of my problems with FXM… Continue reading “My problems with Sitecore FXM”

My problems with Sitecore FXM

Azure Backup fails due to Content Testing Screenshots not clearing

We had a problem with Sitecore 9.0.2 in a PAAS environment. Our Azure App Service backups started failing. This was due to the backup size:Failed Backups

Above 10GB you have to use an Azure Storage Account to store your backup, apparently. However, we wondered why our backups had grown so large – they had been a few GB – and why they seemed to be growing. Continue reading “Azure Backup fails due to Content Testing Screenshots not clearing”

Azure Backup fails due to Content Testing Screenshots not clearing

Why I don’t like Google Tag Manager

Google Tag Manager (GTM) is a tool that lets marketers put code for tracking users/analytics onto a website without having actually change the code of the website. Essentially, Google Tag Manager will inject the code, after the page has loaded. “Tags” in this instance aren’t just #hashtag, but are snippets of code that can record data and send it to third party services.

The advantage of this is that Marketers can put JavaScript code into your production website without needing a developer, and that is genuinely useful to them. However… it’s allowing marketers to put code into your live website! Continue reading “Why I don’t like Google Tag Manager”

Why I don’t like Google Tag Manager